Prior self-sealing composite and unitary roofing and siding shingles generally employ heat and/or pressure sensitive globules, dabs, stripes or bands of adhesive on their under surfaces to aid in securement between courses when shingles are installed.
After manufacture, self-sealing shingles are stored or shipped to the consumer in bundles generally comprising more than 5 units after which the bundles may be stacked and subjected to extended storage at the construction site. Adhesive materials sealing at low temperatures are relatively soft and unable to withstand loads during storage and shipping without deformation and loss of thickness due to compression. The same affect has been noted with other adhesive materials such as the pressure sensitive and higher temperature sealants, although to a lesser extent. In all cases, the loss of adhesive thickness as a result of compression seriously degrades the product performance, most particularly in wind lift resistance of the shingle and tolerable shear strain capacity in the adhesive which causes cracking and other aging problems.
Accordingly it is an object of the present invention to provide a shingle having a load relief zone which would transfer the load on the surface of the adhesive to the entire body of the shingle.
Another object of the invention is to provide a shingle capable of withstanding heavy loads without adhesive deformation.
Still another object of the invention is to achieve the above benefits without altering adhesive formulations currently in use.
Yet another object is to accomplish the above improvements by a commercially feasible and economical method of manufacture.
These and other benefits of the invention will become apparent from the following description and disclosure.